Conversion of PSD, which means Photoshop Document, to PDF, or Portable Document Format, is a crucial task for designers, photographers, and businesses looking to present or share visual content in an adaptable and universally accessible format. PSD files keep images in layers; this is why they are usually perfect for making detailed graphics but has its drawbacks - PSD files are normally sizeable and have limited compatibility. 
Convert such files to PDF so the designed detail, layers, or layout of the design may not be lost but appear quite easily on different kinds of devices and operating systems.
PSD to PDF conversion changes the intricate details of a layered PSD file into a static, transportable format without reducing its quality. The biggest strength of PDFs is that it can be used in print media, presentations, and online documents because it keeps the original design elements intact and is lightweight. A PSD to PDF conversion maintains the layers, color, and resolution and makes it a good option to share files without any problems of compatibility or losing any detail.
Among these tools and software are Adobe Photoshop, Adobe Acrobat, and online conversion tool, which can convert the PSD file to PDF. Adobe Photoshop gives a simple "Save As" where users can choose a PDF output format with options like compression, flattening of layers, and a color profile. This will result in the highest quality output while preserving individual layers if needed.
The major advantages of converting PSD to PDF are in terms of accessibility, file security, and shareability. PDFs are compatible with most devices, easily password-protected, and secure. PDFs are also printable and fantastic for portfolios, client presentations, and digital distribution since they give a polished and professional look.
Refrence: https://smallpdffree.com/psd-to-pdf/